ORIGINAL PAPER

Sexual Plant Reproduction

, Volume 11, Issue 4, pp 213-230

First online:

Sexual and apomictic development in Hieracium

  • A. M. KoltunowAffiliated withC.S.I.R.O. Plant Industry, PO Box 350, Glen Osmond, South Australia 5064 e-mail: anna.koltunow@pi.csiro.au Fax +61-8-83038601
  • , Susan D. JohnsonAffiliated withC.S.I.R.O. Plant Industry, PO Box 350, Glen Osmond, South Australia 5064 e-mail: anna.koltunow@pi.csiro.au Fax +61-8-83038601
  • , Ross A. BicknellAffiliated withCrop and Food Research, Christchurch, New Zealand

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access

Abstract

 Most members of the genus Hieracium are apomictic and set seed without fertilization, but sexual forms also exist. A cytological study was conducted on an apomictic accession of H. aurantiacum (A3.4) and also H. piloselloides (D3) to precisely define the cellular basis for apomixis. The apomictic events were compared with the sexual events in a self-incompatible isolate of H. pilosella (P4). All plants were maintained as vegetatively propagated lines each derived from a single plant. Sexual P4 exhibited characteristic events of polygonum-type embryo sac formation, showed no latent apomitic tendencies, and depended upon fertilization to set seed. In contrast, D3 and A3.4 were autonomous aposporous apomicts, forming both embryo and endosperm spontaneously inside an unreduced embryo sac. The two apomicts exhibited distinct mechanisms, but variation was also observed within each apomictic line. Seeds from apomicts often contained more than one embryo. A degree of developmental instability was also observed amongst germinated seedlings and included variation in meristem and cotyledon number, altered phyllotaxis, callus formation, and seedling fusion. In most cases abnormal seedlings developed into normal plants. Such phenomena were not observed following germination of hybrid seeds derived from crosses between sexual P4 and the apomictic plants. The three plants can now be used in inheritance studies and also to investigate the molecular mechanisms controlling apomixis.

Key words Apomixis Apospory Hieracium Seed Sexual processes